The overall goal is to understand how vascular cells, particularly endothelial cells and smooth muscle cells, are regulated to release arachidonic acid from phospholipids and to synthesize prostacyclin, a vasodilator and a potent physiological inhibitor of platelet aggreation. We will approach this in a systematic way, starting at the very first step, the agonist-receptor interaction. The specific aims are: ---First, to study and characterize the interaction of bradykinin and its receptor in endothelial cells by studying the binding of [3H]bradykinin to these cells. ---And then to investigate the role of polyphosphoinositide and its metabolites inositol-1,4,5-triphosphate and 1,2-diacylglycerol in agonist-induced arachidonic acid release from phospholipids in endothelial cells. ---Examination of the role of phospholipase A2 and phospholipase C in the release of arachidonic acid from phosphatidylinositol in endothelial cells. ---To further our understanding of phosphatidylinositol-hydrolyzing phospholipase A2 by isolation and characterization of this enzyme from endothelial cells. ---Determination of the site(s) of inhibition in arachidonate cascade by phosphodiesterase inhibitors in endothelial cells. ---Study of the regulation of PIG2 synthesis in cultured vascular smooth muscle cells, another important cellular component of the vessel wall. We anticipate that these studies will provide information on the control mechanism of prostacyclin synthesis in vascular cells. This information may further our understanding of the interrelation among endothelial cells, smooth muscle cells and platelets, and of their roles in normal hemostasis and pathophysiology of thrombosis and atherosclerosis, and thereby may ultimately offer potential treatment and control of these diseases.